The objective of this research proposal is to study various factors governing the efficiency of synaptic transmission at the cholinergic synapse. Experiments will be carried out using low frequency (less than 10 Hz) transmitting to high frequency (200-600 Hz) transmitting synapses, a wide range of which can be found in the nerve-electroplaque junction of several electric fish. Synaptic transmission at high frequency has definite implication with regard to biochemical and bioelectrical mechanisms which may be different from that found in low frequency transmission. By this study, therefore, some basis of understanding transmission efficiency may be obtained. The synthesis of acetylcholine, its storage, mobilization, release,replenishments, as well as postsynaptic activation, densensitization and transmitter destruction by enzyme will be studied comparatively using electrophysiological combined with electronmicroscopical and biochemical techniques.